1. Field of the Invention
The present invention relates to a method for fabricating a full-color-displaying liquid crystal display device improving the display quality by trimming a color filter on a transparent substrate to form an opaque film (black matrix) around the color filter and thereby eliminating stray light.
2. Description of the Related Art
An art has been known so far which improves the display quality by forming an opaque film (black matrix) around each color filter on a transparent substrate and thereby eliminating stray light in the fabrication process of a full-color-displaying liquid crystal display device as disclosed in the official gazette of, for example, Japanese Unexamined Patent Publication No. 282223.
The outline of the prior art is described below. First, a transparent electrode linearly extending at a certain pitch is formed on one side of a transparent substrate made of glass or the like to form a photoresist layer on the transparent-electrode formed plane, thereafter a mask having a plurality of slits is superposed on the photoresist layer to apply exposure light from the mask side and develop the layer, and then undeveloped photoresist is removed to leave a stripe-like photoresist layer crossing a plurality of transparent electrodes. Then, R (red), G (green), and B (blue) color filters are superposed on exposed transparent electrodes with no stripe-like photoresist layer formed on them by the electrodeposition method, coloring method, or printing method and baked and cured. Then, the stripe-like photoresist layer is removed by an alkali solution or the like and thereafter, a photoresist layer containing black pigment (so-called black resist layer) is formed on the color filter formed plane (transparent electrode formed plane) of the transparent substrate to develop the layer by applying exposure light from the back, and finally a matrix-like opaque film is formed at gap portions around the color filters by removing unexposed black resist.
However, to form an opaque film (black matrix) around a color filter by the above conventional method, there are problems that the fabrication process is complicated and the cost is inevitably increased because exposure and development of a photoresist layer must be performed twice respectively.
Moreover, the above conventional method has a problem that, because photoresist having a heat-resistant temperature of approx. 150.degree. C. is heated up to approx. 250.degree. C. when baking a color filter, the photoresist causing seizing in the baking step adheres to the surface of a transparent electrode and it is not easily removed. That is, because exposed photoresist changes to gray in color, if a part of a stripe-like photoresist layer remains, photoresist (black resist) thereafter formed is locally insufficiently exposed, a defective opaque film is formed around the color filter, and resultingly the display quality is deteriorated.